Recycled reclaimed asphalt pavement (“RAP”) is asphalt pavement that has been removed from a surface, mixed with additives and reapplied to a surface. Recycling RAP via the Cold Central Plant (“CCP”) process has been performed for many years by various departments of transportation and roadway authorities. CCP-produced recycled RAP has been used for various purposes, including shoulder widening, pothole patching and as a base material. However, CCP-produced recycled RAP has not been considered appropriate for use as a wearing course because it lacks the required structure and density. Reasons for these shortcomings include deficiencies in the asphalt emulsions used in the recycling process, improper manufacturing techniques, stockpile management and application, and deficiencies in the design process.
CCP-produced recycled RAP has often been stored in outdoor stockpiles after processing and then used as needed. However, CCP-produced recycled RAP has rarely been stockpiled for longer than 3 months because it does not remain “lively,” that is, with a high content of uncured, unbroken asphalt.
RAP has also been recycled using asphalt emulsions or “cutbacks” that contain volatile solvents, such as diesel fuel or kerosene, which have been considered necessary to rejuvenate the latent oxidized asphalt in the RAP and to extend stockpile life. However, the solvents proved to be harmful to the environment and to workers involved in their production and use. Further, use of volatile solvents creates added costs that limit the cost-effectiveness of the RAP recycling process.
Additionally, the variety and size of conventional recycled RAP particles has limited the efficacy and predictability of recycling RAP. Recycled RAP formulations having more predictable compositions, fewer or no volatile solvents, and longer stockpile life, along with methods of making and using the same, are needed.
In previous formulations of recycled RAP, the amount of emulsion is typically 3-3.5%, and greater than 2.75%.
The information included in this Background section of the specification is included for technical reference purposes only and is not to be regarded as subject matter by which the scope of the description is to be bound or as an admission of prior art.